Human Health Risk Assessment of Heavy Metal Contaminated Food Crop from Farmlands in Artisanal Refining Areas in Parts of Rivers State, Niger Delta
By Solomon M. P., Agbagwa, I. O., Osuji, L. C.
Farmlands near communities in the Niger Delta Region are experiencing increased damage from heavy metals due to various pollution sources, including gas flaring, artisanal refining, agricultural activities, and traffic, among others. The study was aimed at assessing heavy metal contamination in food crops and soil and the potential risk for residents in Rivers State. Soil and cassava samples from the areas near the artisanal refining areas were sampled and analysed. Plant and soil samples were digested following standard procedures and subjected to atomic absorption spectrophotometric (AAS) analysis. The results indicate that the anthropogenic artisanal refining activities have caused local agricultural soil contamination with Pb, Cd, Ni, Cu, Zn, Hg and Mn in the ranges of 4.49–5.87 mg/kg, 2.37–3.11 mg/kg, 5.10–6.02 mg/kg, 3.54 – 6.72 mg/kg, 6.87 – 13.37 mg/kg and 118.8–156.5 mg/kg, respectively. GIS-based mapping shows that soil heavy metal concentrations were higher in samples collected at the polluted areas than samples taken from non-polluted (Control) areas. The concentrations of Pb, Ni, Cu, Zn, Hg and Cd found in cassava tubers (Manihot esculenta) were in the ranges of 0–0.33 mg/kg, 0.13–0.33 mg/kg, 0.36 – 0.82 mg/kg, 1.55 – 2.58 mg/kg, 12.06 – 34.61 mg/kg and 14.53–65.08 mg/kg, respectively. Most of these concentrations exceeded their maximum permissible limits for contaminants in foods as stipulated by USEPA. Food consumption, soil ingestion and soil dermal exposure are the three routes that contribute to the average daily intake dose of heavy metals for local adults. Moreover, the total hazard indices of Cu, Pb and Cd are greater than the safety threshold of 1.